(1) Field of the Invention
This invention relates to a process for the preparation of carbonyl sulfide by reacting carbon monoxide with sulfur in the vapor phase within a reactor, in which at least the inner surface is made of a special chromium-nickel alloy.
(2) Description of the Prior Art
Carbonyl sulfide is useful as raw material for the production of pesticides, pharmaceuticals and other chemicals. Many proposals have been heretofore made to produce carbonyl sulfide. Illustrations of such proposals are a process wherein a mixture of carbon disulfide and carbon dioxide is heated in the presence of a catalyst; a process wherein a mixture of carbon disulfide and sulfur dioxide is heated in a sealed tube; a process wherein a mixture of hydrogen sulfide and carbon monoxide is heated; a process wherein ammonium thiocyanate is treated with sylfuric acid; and a process wherein a mixture of carbon monoxide and sulfure is heated in the vapor phase in the presence or absence of a catalyst. Of these proposed processes, the last-mentioned process, i.e., the process involving the vapor phase reaction of sulfur with carbon monoxide, is said to be the most advantageous.
Several processes are already known wherein sulfur is reacted in the vapor phase with carbon monoxide. For example, German Anslegeschrift No. 1,222,024 discloses a process wherein carbon monoxide is reacted with sulfur in the vapor phase in the absence of a catalyst at a temperature of from 350.degree. to 510.degree. C. U.S. Pat. No. 2,983,580 discloses the vapor phase reaction of sulfur with carbon monoxide effected in the presence of an aluminosilicate catalyst at a temperature of from 500.degree. to 900.degree. F., i.e., from 260.degree. to 483.degree. C. U.S. Pat. No. 3,764,661 discloses a process wherein carbon monoxide is continuously blown into molten sulfur having incorporated therein anhydrous alkali metal sulfide, and then, the resulting gaseous mixture is brought into contact with anhydrous heavy metal sulfide maintained at an elevated temperature. U.S. Pat. No. 4,078,045 discloses the vapor phase reaction of sulfur with carbon monoxide effected in the presence of an alkaline earth metal compound catalyst at a temperature of from 250.degree. to 450.degree. C.
The above-mentioned processes wherein sulfur is reacted in the vapor phase with carbon monoxide generally have a problem such that the purity of carbonyl sulfide produced generally decreases with the lapse of time in a continuous extended operation. This problem is observed more or less whether the vapor phase reaction is effected in the presence or absence of a catalyst. However, the decrease in the purity of carbonyl sulfide produced is more conspicuous in the case where the vapor phase reaction is effected in the absence of a catalyst and at a relatively high temperature.
Furthermore, the above-mentioned patent references are silent on the construction material for the reactor used. It is presumed that most known construction materials are not completely satisfactory in their anticorrosion properties for use us a reactor for the vapor phase reaction of preparing carbonyl sulfide. This is because at a high temperature, the reaction mixture mainly comprised of carbonyl sulfide possesses a conspicuous corrosive action.